Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Allowance for doubtful accounts	$ 2.0	$ 1.5
Common stock, par value (in dollars per share)
Common stock, shares authorized (in shares)	100,000,000
Common stock, shares issued (in shares)	18,479,684
Common stock, shares outstanding (in shares)	18,479,684
Common Class A [Member]
Common stock, par value (in dollars per share)		$ 1
Common stock, shares authorized (in shares)		75,000,000
Common stock, shares issued (in shares)		13,401,938
Common stock, shares outstanding (in shares)		13,401,938
Common Class B [Member]
Common stock, par value (in dollars per share)		$ 1
Common stock, shares authorized (in shares)		25,000,000
Common stock, shares issued (in shares)		5,077,746
Common stock, shares outstanding (in shares)		5,077,746